1. Field
The present disclosure relates generally to a fluid transport system and, in particular, to a fluid transport system configured to have a desired electrical configuration. Still more particularly, the present disclosure relates to a method and apparatus for limiting the flow of electric current, induced by an event such as lightning or an electrical fault, along a fluid transport system and allowing static dissipation along the fluid transport system.
2. Background
A fluid transport system typically includes tubes connected together for moving fluid through the tubes. As used herein, a “fluid” may comprise any number of liquids and/or gases. Fluid transport systems may be used to transport any number of fluids within vehicles, such as, for example, aircraft. A fluid transport system may include groups of tubes connected in series, in parallel, or a combination of the two. In some cases, these tubes may be coupled together using, for example, without limitation, coupling assemblies.
A fuel system is an example of one type of fluid transport system in an aircraft. Some currently available fuel systems comprise fuel tanks comprised of metal and/or composite materials, such as carbon fiber reinforced plastic (CFRP). When used in fuel tanks, fuel tubes comprised of plastic and/or metal materials may be prone to the buildup of electrostatic charge. The buildup of electrostatic charge on a fuel tube may be caused by a number of different factors including, but not limited to, the flow of fuel through and/or around the fuel tube.
When electrostatic charge builds up on a surface of a fuel tube, the fuel tube may be prone to electrical discharge of this electrostatic charge. This electrical discharge may be referred to as “static discharge.” Static discharge may take the form of, for example, an electrical arc from the fuel tube to a nearby structure.
Further, when used in a fuel tank comprised of electrically resistive materials such as, for example, carbon reinforced plastic, fuel tubes comprised of plastic and/or metal materials may also be prone to voltages and currents induced by an electromagnetic event, such as lightning. In some situations, the induced voltages may lead to electrical discharge in the form of electrical sparking and/or arcing from the tubes to one or more nearby structures. Additionally, in some situations, the induced currents may lead to electrical discharge within the connections between tubes.
The voltage and currents induced by lightning may typically be small and within selected tolerances inside the fuel tanks of aircraft having wings comprised of metal materials, such as, for example, aluminum. However, the voltages and currents induced by lightning inside the fuel tanks of aircraft having wings comprised of non-metallic materials, such as, for example, carbon fiber reinforced plastic, may be greater and outside of selected tolerances. In particular, the higher electrical resistance of carbon fiber reinforced plastic as compared to aluminum may cause larger voltages and currents to be induced with respect to the tubes inside the fuel tanks.
Typically, with currently available aircraft, fuel transport systems use metal tubing to transport fuel within fuel tanks. In an aircraft comprised of carbon fiber reinforced plastic, the metal tubing may be prone to induced voltages that may cause undesired electrical discharges. Some currently available methods for reducing the level or intensity of an undesired electrical discharge may include inserting high resistance electrical isolators into the metal tubing. These isolators may be used to constrain the currents and voltages that may be induced by lightning, thereby reducing the level of any undesired electrical discharge that may occur.
However, the weight and expense needed to install metal systems having these isolators may be greater than desired. Part of the cost and expense to install such metal systems with isolators may be the need to protect the metal systems against arcing from the induced voltages remaining in the system after the installation of the isolators.
Additionally, an electrical discharge within a fuel system caused by the buildup of electrostatic charge and/or induced voltages and currents in response to an electromagnetic event such as lightning may present safety concerns. Therefore, it would be desirable to have a method and apparatus that takes into account at least some of the issues discussed above, as well as other possible issues.